1. Field of the Invention
The present invention relates to a coated resin molded-article. More particularly, it is concerned with a coated polyester resin molded-article in which a cured coating is formed on the surface of a desired polyester resin substrate, said coating can be formed on the surface of a polyester resin substrate by a simple process in a short time, has good adhesion to the surface of a polyester resin substrate, permits a polyester resin substrate to be flexible, has good mechanical properties which improve the hardness and scratch resistance of the surface of a polyester resin substrate, and has superior optical, thermal, and chemical properties.
The coated resin molded-article pertaining to the present invention, especially in the case where the resin molded article is a polyester molded article, has good durability on account of the cured coating having the above-mentioned superior properties. Therefore, it will find use in broad application areas including masks used in the production of ICs and printed circuits, base film for printing, base film for magnetic recording media, base film for heat-sensitive transfer recording media, glass substitute, and vacuum electron tubes.
2. Description of the Related Art
A polyester resin, for example, polyethylene terephthalate, has good flexibility, mechanical properties (such as strength), and optical properties. Therefore, it finds use as film and sheet, fiber, and other materials in a wide range of applications.
Another polyester resin, for example, polycarbonate, has high mechanical strength (especially impact strength), heat resistance, and transparency, and is light in weight. Therefore, it is often used as a glass substitute.
Unfortunately, polyester resins are not necessarily satisfactory in surface properties such as hardness, scratch resistance, adhesion resistance, heat resistance, and chemical resistance, when used in certain application areas. For improvement of surface properties, the surface of polyester resin articles are provided with a coating. There has been a demand for the development of a good coating because the improvement of surface properties is important in such application areas as photomask base film used for the production of ICs and printed circuits in the electronics industry, base film used for printing pattern, base film for magnetic recording media and heat-sensitive transfer recording media, and functional coatings to be made on such base film.
There are known, for coating polyester resin molded-articles, material such as acrylic hard coat and silicone hard coat.
The conventional coating materials have some disadvantages when applied to polyester; they do not readily form a coating with good adhesion by a single application (or one coating). To eliminate this disadvantage, it is necessary to treat the surface of the article to be coated by corona discharge or with primer, or to repeat application of the coating twice or more. These additional steps make the coating process more complex and longer.
It may safely be said that heretofore there was no coated resin molded-article in which good coating was formed on the surface of polyester molded-article by a single application of a coating material without any preliminary surface treatment.
Even though it was possible to form a suitable coating on the surface of polyester molded article by repeated application, the resulting polyester molded article had its inherent shortcomings mentioned below.
In the case where polyethylene terephthalate (a kind of polyester) is used as a base film for ink ribbon, it is provided with a backing layer (on the opposite side of the ink layer) which is formed by the application of a coating material of thermosetting silicone. This backing layer is necessary to prevent blocking and sticking. A disadvantage of the ink ribbon with backing layer is that some components in the backing layer migrate into the ink layer when the ink ribbon is left wound for a long period of time. The result of such migration is that the ink ribbon does not print sharp and clear letters.
Also, in the case where polyethylene terephthalate is used as base film for audio and video magnetic tape, it is provided with a backing layer, on the opposite side of the magnetic layer, for the purpose of smooth tape running. A disadvantage of magnetic tape of this type is that adhesion between the base film and the backing layer is not sufficient and the backing layer is not satisfactory in scratch resistance and durability.
Polyester resins (such as polyethylene terephthalate, polybutylene terephthalate, and polycarbonate) are used for a large variety of containers. Containers of these polyester resins have recently been used for storing petroleum products, chemicals, pesticides, and detergents, or packaging foods and drinks. Some of them, with a food packaged therein are heated in an electronic oven for cooking. These containers, therefore, are required to have good heat resistance, chemical resistance, and surface hardness.
On the other hand, polycarbonate (a kind, of polyester resin) has found use as a glass substitute because of its good mechanical strength (especially high impact strength), heat resistance, and transparency. Applications of polycarbonate include automotive window glass and light cover, building glazing, plastic mirror with metallic film backing, and casings of appliances such as dish washers, humidifiers, coffee makers, sake warmers, and steam irons which use hot water, cold water or steam.
The polycarbonate used as automotive window glass and light cover and building glazing is required to have a cured coating so that it has improved weather resistance, oil resistance, and scratch resistance. An example of the cured coating is one which is formed by irradiating, with ultraviolet rays, a composition composed of acrylate compound, silane compound or silane, silica, and photopolymerization initiator. (See Japanese Patent Laid-open Nos. 131214/1982 and 1756/1983.) However, the weather resistance imparted by such a coating is inferior to that of glass. In addition, the cured coating is liable to hold water droplets when exposed to rain. The water droplets, like lenses, locally intensify the sunlight, causing degradation of the resin molded article. This accelerates the degradation of the originally insufficient weather resistance of the resin molded-article.
Incidentally, it is known that a phosphazene compound which cures upon polymerization is used as a dental filler or adhesive. (See Japanese, Patent Laid-open No. 47406/1986.) This publication discloses a phosphazene compound composed of units represented by the formula below. EQU --[NP (X) (Y)].sub.n --
where n is 3 to 18, preferably 3 and 4; (X)+(Y)=2; (X) and (Y) are each above 0; (X) and (Y) are identical or (Y) is chlorine or a mixture containing chlorine; and (X) is --O(CH.sub.2 R)O.sub.2 CCCH.sub.3 =CH.sub.2 [where R is an alkyl group having 1 to 11 carbon atoms].
According to the disclosure, the phosphazene compound has a high thermal decomposition point and it provides, upon polymerization, a cured product which resembles an inorganic compound in having high rigidity and hardness and a small coefficient of thermal expansion. It is a useful dental resin.
There is disclosed in Japanese Patent Publication No. 2449/1984 a process for producing a polyfunctional (meth)acrylate phosphazene polymer in a non-gel form. According to the disclosure, the process comprises reacting, in the presence of a catalyst, (A) a chlorinated phosphazene polymer containing about 71 wt% or less, preferably about 4 to 55 wt%, of chlorine, with one or more than one functional acrylic monomer selected from the group consisting of (B) acrylamide or methacrylamide, (C) an acrylate or methacrylate having one hydroxyl group, and (D) alkylsubstituted acrylamide or methacrylamide having one hydroxyl group, or further reacting the thus obtained reaction product with one or more than one inert compound selected from the group consisting of (E) a monohydric alcohol having 1 to 18 carbon atoms, (F) a monohydric thioalcohol, (G) a monohydric phenol, and (H) a compound having a primary or secondary amino group. The reaction changes the chlorinated phosphazene polymer into a polyfunctional acrylate or methacrylate phosphazene polymer in a non-gel form of which has at least two acryl or methacryl groups.
The official gazette publication also discloses the following: The (meth)acrylate phosphazene polymer produced according to the process disclosed in the official gazette can be made, upon curing, into a crosslinked polymer, which is an inorganic polymer, having outstanding heat resistance. The polymer is flexible if long-chain (meth)acrylate phosphazene is used as the starting substance Moreover, the polymer has outstanding heat resistance if the above-mentioned inert compound is a halogenated monoalcohol, phenol, or benzyl alcohol. By virtue of these characteristic properties, the (meth)acrylate phosphazene polymer finds use as a coating material and adhesive for a variety of substrates, such as metal, plastics, glass, wood, paper, fiber, and rubber, and also as a raw material or substrate for molded articles, printing inks, printing plates, and gaskets.